Hydraulic driving apparatus



19% l. SUBLETT ET AL 2,731,796

HYDRAULIC DRIVING APPARATUS Filed Feb. 1.7, 1955 4 Sheets-Sheet l Jwmm@Zia &..

Jam. 24, 1955 1. SUBLETT ET AL 2,731,7 6

HYDRAULIC DRIVING APPARATUS Filed Feb. 17, 1955 4 S eets 2 1956 l.SUBLETT ET AL 2,731,796

HYDRAULIC DRIVING APPARATUS HYDRAULIC DREVTNG AEPARATUS Ira Sublett andCharles D. Johnson, Fairrnont, Minn, assiguors to Fairmont Railway Motors, incorporated, Fairmont, Minn., a corporation of Minnesota ApplicationFebruary 17, 1955, Serial No. 488,336

7 Claims. (Cl. 60-51) This invention relates to a hydraulic drivingapparatus and more particularly to an apparatus adapted for use inequipment designed for imparting impact blows or reciprocatory motion,such as, for example, railroad spike drivers, paving breakers, ballasttampers, weed mowers, and the like.

Heretofore in apparatus for such equipment, it has been the customarypractice to utilize pneumatic pressure as the source of power with theresult that such apparatus is possessed of numerous shortcomings. First,the operating etficiency of such apparatus is exceedingly low because ofthe amount of wasted power which is expended. Second, to compensate forthis wasted power, oversize compressors and associated parts arerequired which add materially to the cost and weight of the equipmentand render manipulation of the equipment a difiicult and frequently anawkward operation. Third, the noise, which is normally produced by suchpneumatically operated apparatus, is generally objectionable and isoftentimes disconcerting and fatiguing to the operator, particularlywhere the equipment is being used continuously over extended periods oftime. Lastly, the apparatus had a tendency to frequently get out ofsynchronization, thus requiring considerable service to maintain inproper working order.

Thus, it is an object of this invention to produce an apparatus whichutilizes hydraulic pressure as its source of power and therebyeffectively overcome all of the shortcomings aforenoted.

It is a further object of this invention to produce an apparatus whichis practically foolproof in operation and which enables the operator toexercise complete and positive control of the apparatus at all times.

It is a still further object of this invention to provide an apparatuswhich is compact and simple in construction, thereby facilitatingmanipulation of the apparatus by the operator.

Further and additional objects will appear from the description,accompanying drawings, and appended claims.

In accordance with one embodiment of this invention, a hydraulic drivingapparatus is provided comprising a hydraulically responsivepiston-cylinder unit in which the driving piston thereof has one endthereof protruding longitudinally from an elongated cylinder section.The piston is provided with an enlarged annular boss which is disposedintermediate the ends thereof and is adapted to slidably engage theinterior of such cylinder section and separate the latter into twoisolated compartments, the volumes of which vary upon relative movementof the piston. The protruding piston end is operatively connected to ahydraulic pressure accumulator which is isolated from the cylindersection interior by said piston end and is adapted, at predeterminedtimes, to eifect actuation of said piston in one relative direction. Theaccumulator is in constant communication with a source of hydraulicpressure. Operatively connected to the accumulator is an automaticallyadjustable control valve which, in turn, has a States Patent firstportion thereof operatively connected to an interior portion of thecylinder section disposed, with respect to the accumulator, on theopposite side of the boss formed on the piston, a second portionoperatively connected to a reservoir for hydraulic fluid, and a thirdportion in constant communication with the source of hydraulic pressure.The control valve is biased to normally assume a first position ofadjustment wherein the aforenoted interior portion of the cylindersection and the reservoir are interconnected and the driving piston isactuated by the accumulator pressure in the one relative direction. Thepiston, upon reaching a predetermined station of travel in the onerelative direction, automatically causes the valve and accumulator toeffect communication with one another whereby said valve is actuated bysaid accumulator pressure to a second position of adjustment. Thecontrol valve, when in a second position of adjustment, effectsinterconnection of the aforenoted interior portion of the cylindersection and the source of hydraulic pressure and results in thedirection of movement of the piston being automatically reversed. Uponthe piston reaching a predetermined station while traveling in thereverse direction, communication between said accumulator and valve isautomatically interrupted whereupon said valve returns to its normalposition of adjustment, and the cycle of operation is repeated.

For a more complete understanding of this invention, reference should bemade to the drawings wherein:

Figure 1 'is a fragmentary elevational view of the improved apparatus;

Fig. 2 is a sectional view taken along line 22 of Fig. 1;

Fig. 3 is an enlarged fragmentary sectional view taken alongline 3-3 ofFig. 2;

Fig. 4 is a fragmentary sectional view taken along line 4-4 of Fig. 2;

Figs. 5, 6, and 7 are sectional views taken along lines 5-5, 6-6, and77, respectively, of Fig. 3; and

Figs. 8, 9, l0, and 11 are diagrammatic views of the improved apparatusand the associated parts therefor, showing the piston in four stationsof travel.

Referring now to the drawings and more particularly to Figs. 1 and 2,the improved hydraulic driving apparatus 20 is shown which, asheretofore mentioned, is adapted for use in equipment designed forimparting impact blows or reciprocatory motion. By way of example, andfor purposes of simplification, the description of the apparatus tofollow hereinafter will be in relation to a railroad spike driver. It isto be understood, of course, that the scope of this invention is not tobe confined to this particular type of equipment but is referred tomerely by way of illustration.-

The improved apparatus 20 comprises a hollow housing 21 and piston 22mounted for reciprocatory movement within a chamber 23 formed in thecenter section 23 of the housing. The center section 23 will behereinafter referred to as a cylinder section. The section 23' has theupper end thereof terminating in an annular collar 24 provided with acenter opening 25 through which the upper end portion 22a of the pistonis adapted to extend. A very small tolerance exists between the diameterof the opening 25 and the outside diameter of piston end portion 22a;thus, the latter effects a seal between the interior 23 of cylindersection 23' and a chamber 26 formed in the upper section 27 of thehousing 21 while at the same time the piston is free to reciprocate. Itis to be noted in Figs. 1 and 2 that the outer periphery of housingsections 23 and 27 are provided with a plurality of cooling fins 28which effectively dissipateanyheat which might develop within chambers23 and 26 during movement of the piston.- Other means may be utilized,if desired, to

effect such heat dissipation; for example, the housing sections 23 and27 may be water-jacketed.

Secured to the upper end of housing section 27 is a hydraulic pressureaccumulator 29, the interior of which communicates with chamber 26. Theaccumulator may be of conventional construction well known to thoseskilled in the art.

Chamber 26 is adapted to be in continuous or uninterrupted communicationwith the source of hydraulic pressure 30, see Figs. 8-11, by means of aconduit 31, thereby insuring that the pressure within the accumulator 29will be rapidly replenished once such pressure has been utilized toactuate the piston 22 in one relative direction in a manner to behereinafter more fully described. Conduit 31 is diagrammaticaly shown inFigs. 8ll as being a single pipe; however, in the mechanicalconstruction, shown in Fig. 2, conduit 31 comprises a first passageway31a formed partly in housing sections 27 and 23 and having only one endthereof communicating with the chamber 26 formed in housing 27 and theother end thereof communicating with an aligned passageway 31b formed ina valve housing 32. Valve housing 32 forms a part of a shuttle typecontrol valve 33 which will be described more fully hereinafter.Passageway 31b, formed in valve housing 32, communicates with a secondpassageway 34 formed in said housing which, in turn, terminates in afluid intake port 35. Connected to port 35 is a conduit or pipe 36leading to the source of hydraulic pressure 30, shown in Figs. 8-11.

Mounted on a flattened surface 27a provided on the outside of housingsection 27 is an on-off valve 37 which must be moved to its on positionbefore move ment of the piston 22 can be effected. Valve 37 includes ahollow casing 38 which is secured to housing section 27 by a pluralityof bolts 40. Disposed within an elongated chamber 41, formed withincasing 38, is an elongated shuttle 42 which is adapted to be movedendwise within said chamber 41. Communicating with chamber 41 atsubstantially the longitudinal center thereof is a first passageway 43which, in turn, is aligned with a passageway 44 formed in housingsection 27. Passageway 44 terminates at a small cavity or compartment 45which, during certain stations of travel of piston 22, is in directcommunication with chamber 26. An annular shoulder 46 separates chamber26 and compartment 45 and is provided with an opening 47 which is ofsuch dimension as to permit the upper end 22a of the piston 22 to passthere through. When piston end portion 22a is disposed within opening47, compartment 45 is isolated from chamber 26.

Communicating with chamber 41 and spaced from passageway 43 is a secondpassageway 48 formed in casing 38 which, in turn, is aligned with an endof a passageway 50 formed in housing section 23'. Passageway 50 isspaced from chamber 23 and effects communication between on-off valve 37and a passageway 51, formed in valve housing 32. Passageway 50communicates with an elongated chamber 52 formed in housing 32. Chamber52 is adapted to accommodate therein an elongated shuttle 53 which formsa part of control valve 33. Valve 33 will be described more fullyhereinafter.

Shuttle 42 of on-ofl valve 37 is provided with an annular groove 42awhich is adapted, when the shuttle is actuated to its on position, toeffect interconnection between passageways 43 and 48 of casing 38. Whenshuttle 42 is in its normally off position, as shown in Fig. 2,interconnection of passageways 43 and 48 is interrupted by the shuttle.Shuttle 42 is provided with an integral elongated end section 54 whichis reduced in size and extends axially from the upper end of theshuttle, as seen in Fig. 2, and is enclosed within a cup-like member 55.Encircling end section 54 is a coil spring 56 which has the lower endthereof contacting a stationary washer 57 held in place by a bushing 58,which, in turn, contacts valve casing 38, and an interior shoulderformed in member 55. The other end of the spring 56 engages a retainer60 which is aflixed to the end of section 54 and is movable therewith.Formed in the outer end of member 55 is a port 61 which is adapted toreceive a conduit 62, see Figs. 8-11, leading to a hand or foot-operatedhydraulic piston unit 63. Upon actuation of the piston 63a of unit 63 ina downward direction as viewed in Figs. 8-11, hydraulic pressure isexerted on the large diameter of shuttle 42 and will be of suchmagnitude as to overcome the bias of spring 61 and eflect compressionthereof so as to move the shuttle to the second position of adjustment.Thus, so long as the operator manipulates the unit 63, the apparatuswill operate in a manner to be hereinafter described.

The control valve 33, as heretofore mentioned, is provided with ahousing 32 which is secured by a plurality of bolts 64 to a flattenedsurface 65 formed on the exterior of housing cylinder section 23'beneath flattened surface 27a. Housing 32 is provided with a passageway66 which extends substantially transversely from the longitudinal centerof chamber 52 and is aligned with a passageway 67 formed in housingcylinder section 23'. The passageway 67 terminates in the lower end ofchamber 23. Disposed within passageway 67 is a restrictive valve 68which restricts the flow of fluid only when the latter is moving in adirection toward chamber 23. The reason for this one way restrictiveaction will become apparent hereinafter.

Formed in valve housing 32 is another passageway 70 which terminates atone end in an outlet port 71, the latter being connected by a pipe 72 tothe reservoir 73 for the hydraulic fluid, see Figs. 8-ll. A vent 74 isformed in housing 32 which interconnects the lower end 52a of chamber 52and passageway 70. Communicating with the inner end of passageway 70 andchamber 52 and ex tending angularly therefrom is a passageway 75, seeFig. 4, which, in turn, communicates with the lower end of an elongatedpassageway 76 formed in cylinder section 23, see Fig. 3. The passageway76 is substantially diametrically opposite passageway 31a with respectto chamber 23. The upper end 76a of passageway 76 terminates at theupper end of chamber 23 adjacent annular collar 24 thereby providing acommunication between the upper end of chamber 23 and the reservoir 73at all times.

Disposed within the lower portion 52a of chamber 52 of valve housing 32is a coil spring 77 which is adapted to exert an upward force, as viewedin Fig. 2, on shuttle 53 of valve 33.

The driving piston 22, as heretofore mentioned, is mounted forreciprocatory movement within housing 21. The upper end portion 22a isreduced in cross section and is adapted to be disposed in chambers 26and 23. The lower end 22b of piston portion 22a is slightly reduced incross-sectional size and then flares outwardly and terminates in anenlarged annular boss 220, the

outer periphery of which is substantially the crosssectional size ofchamber 23. The reason for such unique configuration of piston 22 willbecome apparent from the description to follow hereinafter. As thepiston 22 reciprocates the boss 22c is confined to movement withinchamber 23 and effects separation of said chamber into two isolatedupper and lower compartments which vary in volumetric size as the pistonmoves, see Figs. 8-11. The lower end portion 22d of piston 22 extendsdownwardly from the opposite side of boss 220. End portion 22a isrelatively larger in cross section than upper end portion 22a, and isadapted to strike, upon approaching the lower end of its downwardstroke, a driving stud 78 supported at the lower end of housing 21. Thestud 78, in turn, is adapted to engage the head of a spike or the like,not shown. As heretofore mentioned, the apparatus may be used in othertypes of equipment than in a spike driver, and therefore the inventionis not to be limited to a spike driver, A bushing 80 is positioned atthe lower end of chamber 23 and is adapted to properly align the pistonwithin the housing 21 and also to provide a seal for the lower end ofchamber 23.

Operation of apparatus To facilitate understanding of the operation ofthe improved apparatus, reference should be made to Figs. 811 whereinthe direction of movement of the piston at the particular station isshown by the arrow.

To commence operation of the apparatus the piston 63a of unit 63 ismanually actuated causing the shuttle 42 of on-oii-valve 37 to beactuated downwardly to an on position as shown in Figs. 8-11.

In Fig. 8, the piston 22 has reached the end of its upward stroke and isin position to be actuated downwardly by the full impact of thehydraulic pressure accumulated in accumulator 29. When the piston is inthis relative position, the shuttle 53 is in its normal biased positionby reason of coil spring 77. The shuttle 53 is provided with a pluralityof axially spaced annular bosses 81a, 81b, and 810, which are adapted toslidably engage axialiy spaced annular collars 82 formed in chamber 52and eflect alignment of the shuttle 53 within the chamber and at thesame time eifect interconnection of certain of the passageways whichcommunicate with the chamber. When the shuttle 53 is in the positionshown in Fig. 8, there is an interconnection between passageways 67 and72 which results in the lower end of the cylinder chamber 23 beingvented to reservoir 73 and simultaneously therewith the flow of highpressure fluid is blocked by bosses 81b and 81c of valve 33. Because ofthe reduced piston portion 22b, fluid which had previously beenentrapped in compartment 45 is likewise vented to the reservoir 73through collar opening 25 into the upper portion of chamber 23 and thenfrom chamber 23 through passageway 76.

As piston 22 moves from the position shown in Fig. 8 to the positionshown in Fig. 9, piston portion 22a closes off the venting of fluid fromcompartment 45 to chamber 23 and thereby seals any fluid remaining inpassageway 44 and compartment 45. The accumulator pressure plus thepressure from source 30, the latter being relatively insignificant, arethe driving forces which react on piston portion 22a and result indownward movement of the piston.

When the piston 22 reaches the end of its downward stroke, as seen inFig. 10, piston portion 22a moves past collar 46 and effectsinterconnection of compartment 45 and chamber 26 which results in highpressure fluid being introduced into passageway 44, valve 37, passageway50 and chamber 52 of valve 33. The high pressure fluid reacts againstthe upper surface of boss 81c and thereby overcomes the bias of spring77 and causes the shuttle 53 of valve 33 to move to its down positionwithin the valve housing 32, see Figs. and 11. When the shuttle 53 ofvalve 33 is in its down position, high pressure passageway 36 leadingfrom the source 30 is interconnected to passageway 67 and thereby causesthe high pressure fiuid to flow into the lower end of chamber 23 andexert a force on the underside of boss 220 of piston 22 and result inpiston 22 moving upwardly in the direction of the arrow, by reason ofthe undersurface of boss 220 being relatively larger in area than thetop surface of piston portion 22a disposed adjacent accumulator 29. Theflow of the high pressure fluid past restriction valve 68 in a directiontoward chamber 23 is restricted somewhat, as heretofore mentioned,thereby dampening, to a certain extent, the inertia of piston 22 in anupward direction which might ordinarily cause excessive rebound andshock of the piston when the latter reaches the end of its upwardstroke.

As piston 22 moves from the position of Fig. 10 to the position of Fig.11, piston portion 22a once again isolates compartment 45 from chambers26 or, 23 and thereby results in shuttle 53 of valve. 33 being locked inits down position by the entrapped hydraulic fluid until venting ofcompartment 45 into chamber 23 occurs, as shown in Fig. 8, whereuponshuttle 53 returns to its normal upposition clue to the bias of spring77. The cycle of operation of piston 22 will repeat itself and continueto do so until the operator releases his grip on unit 63 and on-oflvalve 37 automatically returns to its ofFposition.

Thus, it will be seen that an improved hydraulic driving apparatus hasbeen provided wherein the operation of piston 22 and the shuttle 53 ofvalve 33 will remain in perfect synchronous relation at all timesbecause the movement of the latter is dependent upon the movement of theformer and thereby such synchronous relation insures foolproofperformance of the apparatus. Furthermore, the apparatus is compact inconstructionand of a closed circuit design, thereby facilitatingmanipula tion and handling of the apparatus. In addition the apparatusresults in eflicient utilization of the source of hydraulic pressure andthereby elfects a saving in operat ing costs.

While a particular embodiment of this invention is shown above, it willbe understood, of course, that the invention is not to be limitedthereto, since many modifications may be made, and it is contemplated,therefore, by the appended claims, to cover any such modifications asfall within-the true spirit and scope of this invention.

We claim:

1. A hydraulic driving apparatus comprising a hydraulically responsivereciprocating element, a source of hydraulic pressure, a reservoir forhydraulic fluid, a hydraulic pressure accumulator communicating withsaid source and operatively connected to act on one portion of saidelement to effect at a predetermined time movement of said element inone relative direction, and adjustable means operatively connected tosaid source, said reservoir, a second portion of said element, and saidaccumulator; said means, when in one position of adjustment, beingresponsive to said accumulator pressure and effecting interconnection ofsaid source and said second element portion whereby said element isactuated in a second relative direction'and, when in a second positionof adjustment, being out of communication with said accumulator andeflecting interconnection of said reservoir and said second elementportion whereby said element is actuated in said one direction by saidaccumulator pressure.

2. A hydraulic driving apparatus comprising a hydraulically responsivereciprocating element, a source ofhydraulic pressure, a reservoir forhydraulic fluid, a hydraulic pressure accumulator communicating withsaid source and operatively connected to act on one portion of saidelement to effect at a predetermined time movement of said element inone relative direction, and adjustable valve means operatively connectedto said source, said reservoir, a second portion of said element, andsaid accumulator; said means, when in one position of adjustment, beingresponsiveito said accumulator pressure and effecting interconnection ofsaid source and said second element portion whereby said element isactuated in a second relative direction, and when in a second positionof adjustment, being out of communication with said accumulator andeifecting interconnection of said reservoir and said secondelementportion whereby said element is actuated in said one relativedirection by said accumulator pressure; the adjustment of said meansbeing automatically eflecte d by said element upon the latter reachingpredetermined stations of travel.

3. A hydraulic driving apparatus comprising a hydraulically responsivereciprocating element, a source of hydraulic pressure, a reservoir forhydraulic fluid, a hydraulic. pressure accumulatorcommunicating withsaid source and with one portion of said element to eifect at apredetermined time movement of said element in one relative direction,adjustable first means operatively connected to said source, saidreservoir, a second portion of said element, and said accumulator, saidfirst means, when in one position of adjustment, being responsive tosaid accumulator presure and efiecting interconnection of said sourceand said second element portion whereby said element is actuated in asecond direction, and, when in a second position of adjustment, beingout of communication with said accumulator and effecting interconnectionof said reservoir and said second element portion whereby said elementis actuated in said one direction by said accumulator pressure, and anadjustable second means interposed said accumulator and said first meansfor interrupting the interconnection therebetween when said second meansis in one position of adjustment.

4. A hydraulic driving apparatus comprising a hydraulically responsivereciprocating element, a source of hydraulic pressure, a reservoir forhydraulic fluid, a hydraulic pressure accumulator communicating withsaid source and with one portion of said element to effect at apredetermined time movement of said element in one relative direction,and adjustable valve means operatively connected to said source, saidreservoir, a second portion of said element, and said accumulator; saidvalve means being biased to normally assume one position of adjustmentwherein said means is out of communication with said accumulator whilesaid second element portion and said reservoir are in communication withone another to effect actuation of said element in said one direction bysaid accumulator pressure; said valve means being automatically broughtinto communication with said accumulator and actuated out of its normalposition of adjustment to a second position of adjustment by saidaccumulator pressure upon said element reaching a predetermined stationof travel in said one direction; said valve means, when in said secondposition of adjustment, effecting communi cation of said source and saidsecond element portion whereby said element is actuated in an oppositedirection by the pressure from said source; said valve meansautomatically reverting to its normal position of adjustment upon saidelement reaching a second predetermined station of travel in saidopposite direction.

5. A hydraulic driving apparatus comprising a hydraulically responsivepiston-cylinder unit having one end of the piston thereof protrudingfrom the cylinder and an enlarged boss formed on said pistonintermediate the ends thereof and disposed within said cylinder andeffecting separation of the cylinder interior into two isolatedcompartments, a source of hydraulic pressure, a reservoir for hydraulicfluid, a hydraulic pressure accumulator accommodating the protruding endof said piston and being isolated from the interior of said cylinder bysaid protruding piston end, said accumulator effecting at apredetermined time movement of said piston in one relative direction,and adjustable control means operatively connected to said source andreservoir and in communication with a portion of said cylinder, disposedwith respect to said accumulator, on the opposite side of said pistonboss, for regulating movement of said piston; said means, when in oneposition of adjustment, being responsive to said accumulator pressureand effecting interconnection of said source and said cylinder portionwhereby said piston is actuated in a second relative direction, and,when in a second position of adjustment, being out of communication withsaid accumulator and effecting interconnection of said cylinder portionand said reservoir whereby said piston is actuated in said one relativedirection by said accumulator pressure, the position of adjustment ofsaid control means being automatically effected upon said pistonreaching predetermined stations of travel within said cylinder.

6. A hydraulic driving apparatus comprising a pistoncylinder unitwherein the piston thereof is hydraulically responsive and mounted forreciprocatory movement Within the cylinder of said unit, said pistonhaving one end thereof protruding from said cylinder and having anenlarged boss formed on said piston intermediate the ends thereof andefiecting separation of the cylinder interior into isolatedcompartments, a source of hydraulic pressure, a reservoir for hydraulicfluid, a hydraulic pressure accumulator accommodating the protrudingpiston end and being isolated from the interior of said cylinder by saidpiston end, said accumulator elfecting at a predetermined time movementof said piston in one relative direction, and automatically adjustablecontrol means operatively connected to said source, reservoir,accumulator, and a portion of said cylinder disposed with respect tosaid accumulator on the opposite side of said enlarged piston boss, forefiecting reciprocatory movement of said piston; said control meansbeing biased to normally assume one position of adjustment wherein saidmeans is out of communication with said accumulator and interconnectionof said cylinder portion and said reservoir is effected and said pistonis moved in said one relative direction by said accumulator pressure;said control means communicating with said accumulator and beingactuated out of normal position by said accumulator pressure to a secondposition of adjustment upon said piston reaching a predetermined stationof travel in said one relative direction; said'means, when in saidsecond position of adjustment, interconnecting said source and saidcylinder portion to effect reversal in the direction of relativemovement of said piston, the latter upon reaching a predeterminedstation of travel in said reversed direction effecting interruption ofthe communication between said accumulator and control means whereuponthe latter returns to its normal position of adjustment.

7. A hydraulic driving apparatus comprising a hydraulically responsiveramming piston mounted for reciprocatory movement within a cylinder,said piston having one end thereof protruding from said cylinder andhaving an enlarged annular boss formed thereon intermediate the ends ofsaid piston and disposed Within and slidably contacting the interior ofsaid cylinder to form two isolated compartments within said cylinder, asource of hydraulic pressure, a reservoir for hydraulic fluid, ahydraulic pressure accumulator communicating with said source andaccommodating the protruding piston end and exerting at predeterminedtimes accumulated pressure on said accommodated piston end to elfectmovement of said piston in one relative direction, adjustable valvemeans operatively connected to said accumulator, said source, saidreservoir, and a portion of said cylinder disposed with respect to saidprotruding piston end on the opposite side of said boss, said valvemeans being biased to normally assume a position wherein said means isout of communication with said accumulator and said reservoir andcylinder portion are interconnected to efiect movement of said piston insaid one direction, said piston, upon reaching a predetermined stationof travel in said one direction within said cylinder, automaticallyeffecting communication between said accumulator and valve means whereinthe latter is moved from its normal position of adjustment to a secondposition, said valve means, when in said second position, effectinginterconnection of said source and said cylinder portion whereby thedirection of movement of said piston is reversed and said piston isactuated in said reversed direction by the pressure from said sourcebeing exerted on said boss, said piston, upon reaching a predeterminedstation of travel within said cylinder when moving in said reverseddirection, interrupting communication between said accumulat or and saidvalve means whereby the latter returns to its normal position ofadjustment, and a manually operated on-oit control means interposed saidaccumulator and said valve for interrupting communication therebetweenwhen in an off position.

No references cited.

